1. Field of Invention
The present invention relates generally to the field of wireless communication and data networks. More particularly, in one exemplary aspect, the present invention is directed to compensating for or mitigating the effects of electro-magnetic signal interference in devices implementing two or more wireless air interfaces or protocols.
2. Description of Related Technology
The effective implementation of convergence products has led to a revolution in the way consumers view computerized devices. These next generation computerized devices focus on offering consumers a substantially unified solution for a variety of services to which consumers have become accustomed. One example of such a converged solution is the exemplary M82 (“MacBook Air”) laptop computer or iPhone™ each manufactured by the Assignee hereof, which support a variety of wireless protocols and other functions. For instance, the iPhone™ has the capability of, among other things, sending and receiving emails over a wireless LAN (WLAN) network, making and receiving calls using a GSM cellular network, and operating wireless peripheral equipment (such as wireless head sets) using the Bluetooth (BT) protocol.
Converged Device Performance Issues
As technologies converge, implementation requirements and constraints, including cost, size, and antenna isolation in these hardware systems inevitably will introduce difficulties that can potentially result in a poor user experience with the device. For example, both BT and WLAN (802.11b/g/n) share the same ISM band in the 2.4-2.8 GHz frequency range. Due to the close physical proximity of these wireless interfaces (including their antenna) in these converged or unified devices, the BT and WLAN technologies can interfere with each other when operating simultaneously, and can cause problems such as for example BT audio stutter and drop-outs, slow WLAN transfer speeds, poor BT mouse tracking, etc.
Several solutions have been contemplated in the prior art to address the co-existence problems of co-located or proximate wireless technologies. For example, United States Patent Publication No. 20070099567 to Chen; et al. published May 3, 2007 and entitled “Methods and apparatus for providing a platform coexistence system of multiple wireless communication devices” discloses various embodiments of methods and apparatus for providing a platform coexistence system of multiple wireless communication devices.
United States Patent Publication No. 20070080781 to Ginzburg; et al. published Apr. 12, 2007 and entitled “Device, system and method of coordination among wireless transceivers” discloses devices, systems and methods of coordination among wireless transceivers. For example, an apparatus in accordance with an embodiment of the invention includes first and second wireless transceivers, wherein the first wireless transceiver is to enter a non-transmission mode for a pre-defined time period in response to an indication from the second wireless transceiver, and wherein one of the first and second wireless transceivers is to operate in a synchronous network and the other of the first and second wireless transceivers is to operate in a non-synchronous network.
United States Patent Publication No. 20070060055 to Desai; et al. published Mar. 15, 2007 and entitled “Method and system for antenna and radio front-end topologies for a system-on-a-chip (SOC) device that combines BT and IEEE 802.11 b/g WLAN technologies” discloses a method and system for antenna and radio front-end topologies for a system-on-a-chip (SOC) device that combines BT and IEEE 802.11 b/g WLAN technologies. A single chip radio device that supports WLAN and BT technologies receives a WLAN signal in a WLAN processing circuitry of the radio front-end and in a BT processing circuitry of the radio front-end. Signals generated by the WLAN processing circuitry and the BT processing circuitry from the received WLAN signal may be combined in a diversity combiner that utilizes selection diversity gain combining or maximal ratio combining (MRC). When a generated signal is below a threshold value, the signal may be dropped from the combining operation. A single antenna usage model may be utilized with the single chip radio device front-end topology to support WLAN and BT communications.
United States Patent Publication No. 20060274704 to Desai; et al. published Dec. 7, 2006 and entitled “Method and apparatus for collaborative coexistence between BT and IEEE 802.11g with both technologies integrated onto a system-on-a-chip (SOC) device” discloses a method and system for collaborative coexistence between BT and IEEE 802.11g with both technologies integrated onto an SOC device. In a single integrated circuit (IC) that handles BT and WLAN technologies, a WLAN priority level may be selected for WLAN transmissions and a BT priority level may be selected for BT transmissions. The WLAN and BT priority levels may be selected from a plurality of priority levels. A packet transfer scheduler (PTS) may schedule the transmission of WLAN and BT signals in accordance with the selected priority levels. In some instances, the PTS may promote or demote the priority levels for WLAN and/or BT transmissions based on traffic needs.
United States Patent Publication No. 20060133259 to Lin; et al. published Jun. 22, 2006 and entitled “Interference rejection in wireless receivers” discloses a wireless system which mitigates the effects of interference through updating noise variance estimates. Noise variance estimates may be updated after the reception of a preamble in an OFDM receiver.
United States Patent Publication No. 20060084383 to Ibrahim; et al, published Apr. 20, 2006 entitled “Method and system for co-located IEEE 802.11 B/G WLAN, and BT with FM in coexistent operation” discloses a method and system for co-located IEEE 802.11b/g WLAN, and BT (BT) with FM in coexistent operation are provided. A single chip comprising an integrated BT radio and an integrated FM radio in a coexistence station may generate a priority signal to disable WLAN transmissions in a WLAN radio when a BT HV3 frame is available for transmission. When the priority signal is asserted, an exponentially growing retransmission backoff mechanism in the WLAN radio may be disabled. Moreover, when the BT radio and the WLAN radio are enabled for coexistence operation, a WLAN fragmentation threshold in the WLAN radio may be modified based on a WLAN modulation rate and the BT HV3 frame duration. An on-chip processor that time multiplexes FM and BT data processing may be utilized to control the BT radio operation and the FM radio operation in the single chip.
United States Patent Publication No. 20060030266 to Desai; et al. published Feb. 9, 2006 and entitled “Method and system for achieving enhanced quality and higher through put for co-located IEEE 802.11B/G and BT devices in coexistent operation” discloses a method and system for achieving enhanced quality and higher throughput for co-located IEEE 802.11b/g and BT (BT) devices in coexistent operation are provided. A priority signal may be generated by a BT radio in a coexistence station to disable WLAN transmissions in a WLAN radio when a BT HV3 frame is available for transmission. When the priority signal is asserted, an exponentially growing retransmission backoff mechanism in the WLAN radio may be disabled. Moreover, when the BT radio and the WLAN radio are enabled for coexistence operation, a WLAN fragmentation threshold in the WLAN radio may be modified based on a WLAN modulation rate and the BT HV3 frame duration.
United States Patent Publication No. 20060030265 to Desai, et al. published Feb. 9, 2006 entitled “Method and system for sharing a single antenna on platforms with co-located BT and IEEE 802.11 b/g devices” discloses a method and system for sharing a single antenna on platforms with co-located BT and IEEE 802.11b/g devices. A single antenna may be utilized for communication of BT HV3 frame traffic and wireless local area network (WLAN) communication based on a time multiplexing approach. At least one antenna switch may be utilized to configure an antenna system to enable BT and WLAN coexistence via the single antenna. Configuration signals may be generated by a BT radio device and/or by a WLAN radio device to configure the antenna system. A default configuration for the antenna system may provide WLAN communication between a station and a WLAN access point until BIT communication becomes a priority.
United States Patent Publication No. 20050215197 to Chen, et al. published Sep. 29, 2005 and entitled “Apparatus and methods for coexistence of co-located wireless local area network and BT based on dynamic fragmentation of WLAN packets” discloses an 802.11—enabled device may fragment an 802.11 packet into smaller packets and transmit the smaller packets instead of the 802.11 to lessen interference with BT synchronized connection-oriented communication of a co-located or nearby BT-enabled device.
In another approach, the Cisco Technologies. Inc. Radio Resource Management (RRM) technology is implemented in an Access Point (AP). RRM addresses co-channel interference when two APs use the same channel. In this case, the overall network capacities within these two APs are half of the network capacity if the two channels are assigned with non-overlap channels. The Cisco Dynamic Channel Assignment capability can assign an AP with a different channel to increase network capacity. However, the RRM technology does not address issues with convergence products such as those previously described, and also relies on the AP to manage co-channel interference.
Wireless Network Performance Issues
In addition to interference within a convergence device offering two or more different wireless protocols, the use of these protocols can also affect the performance of the underlying wireless network (e.g. the LAN, PAN, etc.) itself. For example, BT clients operate in the same unlicensed frequency band as other wireless protocol technologies such as Wi-Fi and as multiple BT devices can communicate with a single BT module in the network, BT devices can potentially occupy 100% of the duty cycle for its own PAN network. Further the latest BT technologies only deliver up to about 3 Mbps (extended data rate or EDR, per Bluetooth version 2.0) in the physical layer versus a Wireless LAN device that can easily deliver in excess of 100 Mbps in a Multiple In, Multiple Out (MIMO) system. When two asymmetric or heterogeneous devices exist in the same network (e.g. BT and Wi-Fi), network capacity can often be dominated by the slower device (from the client-side perspective).
Several existing BT stereo headphones operating in Advanced Audio Distribution Profile (A2DP) reserve more bandwidth than is needed for their operation, especially headphones with BT version 1.2 (up to 1 Mbps). As a result, such devices may further reduce network capacity in their operating frequency band that is also shared with the WLAN (assuming that the client prioritizes the A2DP packets). Current network capacity protection schemes, such as a power saving (PS) mode and the CTS2SELF scheme, only work if the BT device has a very limited duty cycle. These schemes cannot prevent BT overuse and misbehavior.
In the context of Wi-Fi, WLAN driver chipsets (such as for example those manufactured by Broadcom, Inc., such as the BCM 4325) typically operate without a power saving mode (e.g., “PM=0”) when the underlying device is connected to a power supply (i.e. a 120V/240V wall outlet), and operate in a power saving mode (“PM=2”) when the device is operating under battery power. Understandably, this default setting has been desirable in the past for most applications as the users of these WLAN driver chipsets want to efficiently manage both de-vice latency and power consumption to maximize the user experience. While these default settings have their benefits, it is noted that in the context of a device which also utilizes BT, the overall network capacity (LAN, PAN, etc.) suffers as a result of using the default settings in many WLAN driver chipsets. WLAN driver chipset makers have attempted to address WLAN/BT coexistence for a co-located system, and they have also provided several solutions to improve network capacity. However, these prior art attempts assume that BT only has an SCO (synchronous connection-oriented) link, which occupies about a third of the total bandwidth, leaving about two-thirds of the bandwidth to the WLAN. The A2DP duty cycle has not been considered under these models, nor has the combination of multiple BT devices connected to the same system. In essence, these prior art approaches have very limited schemes with the primary aim of assuring BT device operation, as opposed to maintaining a certain quality level for the network(s) as a whole.
Accordingly, improved methods and apparatus are needed for enhancing capacity in networks that comprise two or more wireless technologies that at least partly operate in the same frequency bands. Ideally, such improved methods and apparatus would promote the existence of a “good neighborhood” by monitoring the behavior of wireless modules within a given converged device, as well as the behavior of other devices in, the network, and dynamically adjusting operating behaviors in order to benefit the network as a whole. This holistic approach benefits not only the converged device implementing the policies, but also the broader network.
In the context of an exemplary BT/WLAN coexistence device and network(s), such improved apparatus and methods would ideally implement an an aggressive duty cycle control scheme, and improve network capacity and user experience by monitoring factors such as, inter alia: (1) network traffic, including its own network traffic; (2) the number of clients connected to the network access point (AP); (3) the percentage of traffic going to WLAN; (4) the percentage of traffic going to the BT interface; and (5) the device received signal strength indication (RSSI).
Such improved methods and apparatus would also ultimately provide the users of the network with the best use experience possible by dynamically adjusting the client device duty cycle, while offering converged services in a unified client device in a space- and power-efficient manner.